Frequency Agile Filter Using a Digital Filter and Bandstop Filtering

• US 20110227665A1
• Filed: 11/26/2009
• Published: 09/22/2011
• Est. Priority Date: 12/01/2008
• Status: Active Grant

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Wyville, Mark
• Granted Patent: US 8,489,056 B2
• Time in Patent Office: Days
• US Class Current: 333/17.1
• CPC Class Codes: H03H 11/344 Duplexers
• CPC Class Codes: H04B 1/005 adapting radio receivers, transmitters andtransceivers for operation on two or more bands, i.e. frequency ranges
• CPC Class Codes: H04B 1/10 Means associated with receiver for limiting or suppressing noise or interference
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver
• CPC Class Codes: H04B 1/62 for providing a predistortion of the signal in the transmitter and corresponding correction in the receiver, e.g. for improving the signal/noise ratio
• CPC Class Codes: H04L 25/08 Modifications for reducing interference; Modifications for reducing effects due to line faults ; Receiver end arrangements for detecting or overcoming line faults

Abstract

The present invention is a hybrid RF-digital signal processor-based filter for multiband radio architectures, systems capable of spectrum re-farming and software defined radios It performs low-loss frequency agile multiple notch filtering at RF where a large dynamic range exists at a filter input between signals in a stopband and passband It is a frequency dependent signal attenuation apparatus having two paths connected together by directional couplers The first path comprising a component such as a delay component or duplexer The second path comprising, in series, a down converter, a digital filter, an up converter, and a bandstop filter At the output of a power amplifier, the invention can be used to attenuate spurs, or noise within bands with strict emission constraints At the input of a low noise amplifier, the invention can be used to attenuate blockers and transmitter noise outside of the receiver passband.

Claims

1. A frequency dependent signal attenuation apparatus, comprising:

an input signal receiver coupled to a first directional coupler, which splits the input signals into a first signal path and a second signal path,

an RF/Analog 1 frequency down converter coupled to the first directional coupler along the first signal path, the RF/Analog 1 frequency down converter having one or more down converter mixers coupled to a first filter and an analog to digital converter, and said one or more down converters being controlled by a local frequency oscillator signal,

a second filter coupled to the one or more down converter mixers in RF/Analog 1 frequency down converter through the first filter and analog to digital converter in the RF/Analog 1 frequency down converter,

an RF/Analog 2 frequency up converter coupled to the second filter, which has one or more up converter mixers coupled to the second filter through a third filter and a digital to analog converter, each of said one or more up converters being controlled by a local frequency oscillator signal,

a bandstop filter coupled to the RF/Analog 2 frequency up converter, said bandstop filter provides its output signal to a second directional coupler that also receives a second signal along the second path from the first directional coupler, said signal from the first directional coupler passes through a component before being received at the second directional coupler,

a signal output provided by the second directional coupler that includes recombined signals that have passed through the first and second pathways, said signal from said first signal path attenuates the signal from the second signal path at the second directional coupler.

2. The apparatus in claim 1, wherein said filter is a reconfigurable discrete-time filter.

3. The apparatus in claim 1, wherein said bandstop filter is a notch filter.

4. The apparatus in claim 3, wherein said notch filter is tunable.

5. The apparatus in claim 1, wherein said filter is a programmable digital filter.

6. The apparatus in claim 1, wherein the frequency down converters are frequency agile.

7. The apparatus in claim 1, wherein the frequency up converters are frequency agile.

8. The apparatus in claim 1, further including a circuit that exhibits negative group delay over frequencies where attenuation is desired is placed on the first path.

9. The apparatus in claim 1, wherein said bandstop filter is tunable.

10. A frequency dependent signal attenuation apparatus, comprising:

an input signal receiver coupled to a first directional coupler, which splits the input signals into a first signal path and a second signal path,

an RF/Analog 1 frequency down converter coupled to the first directional coupler along the first signal path, the RF/Analog 1 frequency down converter having one or more down converter mixers coupled to a first filter and an analog to digital converter, and said one or more down converters being controlled by a local frequency oscillator signal,

a second filter coupled to one or more down converter mixers in RF/Analog 1 frequency down converter through the first filter and analog to digital converter in the RF/Analog 1 frequency down converter,

an RF/Analog 2 frequency up converter coupled to the second filter, which has one or more up converter mixers coupled to the second filter through a third filter and a digital to analog converter, each of said one or more up converters being controlled by a local frequency oscillator signal,

a bandstop filter coupled to the RF/Analog 2 frequency up converter, said bandstop filter provides its output signal to a second directional coupler that also receives a second signal along the second path from the first directional coupler, said signal from the first directional coupler passes through a component element before being received at the second directional coupler, a signal output provided by the second directional coupler that includes recombined signals that have passed through the first and second pathways, and,

a third directional coupler coupled to the second directional coupler, which provides a signal to an RF/Analog 3 frequency down converter, said down converter providing a signal to a controller that provides a feedback control signal to the filter.

11. The apparatus in claim 10, wherein said filter is a reconfigurable discrete-time filter.

12. The apparatus in claim 10, wherein said bandstop filter is a notch filter.

13. The apparatus in claim 12, wherein said notch filter is tunable.

14. The apparatus in claim 10, wherein said filter is a programmable digital filter.

15. The apparatus in claim 10, wherein the frequency down converters are frequency agile.

16. The apparatus in claim 10, wherein the frequency up converters are frequency agile.

17. The apparatus in claim 10, further including a circuit that exhibits negative group delay over frequencies where attenuation is desired is placed on the first path.

18. The apparatus in claim 10, wherein said bandstop filter is tunable.

19. A method of providing a frequency dependent attenuated signal comprising the steps of:

receiving an input signal at a first directional coupler,

splitting the input signal at the first directional coupler into a first signal path and a second signal path,

receiving a signal along the first signal path at an RF/Analog 1 frequency down converter coupled to the first directional coupler, the RF/Analog 1 frequency down converter processing the received signal with one or more analog to digital converters, one or more down converter mixers and a first filter,

providing an output signal from the RF/Analog 1 frequency down converter to a second filter, which processes and filters the signal provided on the first signal path,

receiving the output of the second filter at an RF/Analog 2 frequency up converter, which processes the signal in one or more digital to analog converters, one or more up converter mixers, and a third filter,

providing the signal from the RF/Analog 2 frequency up converter to a bandstop filter,

providing a signal from the bandstop filter to a second directional coupler;

combining at the second directional coupler the output of the bandstop filter with a signal from the first directional coupler that passes through a component before being received at the second directional coupler, said combined signal produced at the output of the second directional coupler is said signal from said first signal path attenuated by the signal from said second signal path.

20. The method of claim 19 further comprising the steps of:

providing the first output signal to a third directional coupler, which provides a signal to an RF/Analog 3 frequency down converter, and,

providing a feedback signal from the RF/Analog 3 frequency down converter to a controller that provides a feedback control signal to the filter.

21. The method of claim 20 further comprising the steps of:

providing a second output signal from the third directional coupler.

22. The method of claim 19 wherein said second filter is a reconfigurable discrete-time filter.

23. The method of claim 19 wherein said second filter is a programmable digital filter.